An Informational Brief on Polymer Machining
Kynar®, Polyvinylidene Difluoride (PVDF) is a specialty fluoropolymer thermoplastic known for its ease of processing and its versatility in a variety of applications. PVDF’s manufacturing not only ensures durability in its utility, but also delivers an innate resistance to acids, bases, high temperatures, and solvents. Harsh industrial environments are no match for PVDF parts, which is why it is commonly used in environments requiring extreme resistance to a broad range of chemicals.
Additional demand for fluoropolymers like Kynar® PVDF is driven by the increasing trend of specialized, small-batch production for customized parts and components. Companies developing prototypes find it extremely convenient to have access to a fluoropolymer part manufacturer such as AIP. Furthermore, AIP’s experience with custom-engineering plastics ensures our customers’ evolving needs are always met with the same level of innovation and excitement for creating new ways to deliver value in fluoropolymer applications.
Our latest machining guide discusses what goes into machining PVDF and how its considerations differ from other manufacturing options such as metal machining, injection molding, and 3D printing.
How does AIP approach PVDF and its machining process? To start, we’ll explain the difference between machining PVDF, a thermoplastic, and machining thermosets.
Machining Thermoplastics vs Thermosets
We’ve already said that PVDF is a thermoplastic, but what does that mean exactly?
All polymers can more or less be divided into two categories: thermoplastics and thermosets. The main difference between them is how they react to heat. Thermoplastics like PVDF, for example, melt in heat, while thermosets remain “set” once they’re formed. Understanding the technical distinction between these types of materials is essential to CNC machining them properly.
What type of thermoplastic is PVDF in particular? PVDF is a semi-crystalline, high purity engineering thermoplastic, meaning its molecular structure is highly ordered.
Properties & Grades of Machined Kynar® (PVDF)
As a thermoplastic, Kynar® PVDF offers industrial-grade resistance to pH changes due to varying thermal conditions, as well as solvent-resisting capabilities. This can be an advantage in petrochemical industries where fluoropolymer parts are in contact with or exposed to bursts of gases, oil or detergents.
It should also be noted that Kynar® PVDF is known for its high degree of crystallinity, which results in a stronger and strain-resisting component. Add to that a natural resistance to fungus, ozone and weather, which makes Kynar® PVDF a great fluoropolymer for coatings and manufactured parts exposed to the elements.
Finally, adding to its versatile performance in industrial environments, Kynar® PVDF provides excellent resistance to nuclear radiation, allowing it to be used in both Power Generation and military applications.
AIP offers a range of Kynar® and PVDF grades that provide different strength, thermal stability, and corrosion resistance and can help you select the best grade of PVDF for your application..
Machining Kynar® (PVDF)
The process of annealing and stress-relieving PVDF reduces the likelihood of surface cracks and internal stresses occurring in the material. Post-machining annealing also helps to reduce stresses that could potentially contribute to premature failure.
PVDF offers ease of machining and tight tolerances due to its inherent strength, toughness and dimensional stability. Machining PVDF isn’t too different from machining metals as a result of this; pretend you’re machining brass. Unlike metal, though, PVDF (like all thermoplastics) will deform if you hold it too tightly as it yields easily.
We generally recommend Tungsten Carbide Alloy Tooling. Also, keep the part very cool and support it well.
We also suggest non-aromatic, air-based coolants to achieve optimum surface finishes and close tolerances. Coolants have the additional benefit of extending tool life as well.
Case in point, Kynar® PVDF can be manufactured into industrial equipment components that may include piping and tubing, valves, tanks, nozzles, and fittings—among many other formats. It can also be combined with other materials, helping customers innovate and create new product classes with utility that exceeds its original applications.
Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace sciences. To ensure the highest level of sanitation down to the sub-molecular level, AIP Precision Machining designs, heat-treats and machines only plastics, with any sub-manufactured metalwork processed outside our facility. This allows us to de-risk the process from metallic cross contamination.
Kynar® (PVDF) Machining Guide: Supportive Information
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